Manufacture of seamless tubes



Sept. 15, 1931. o. BAMBERGER MANUFACTURE OF SEAMLESS TUBES Filed March 25, 1926 llwuztor' Um I Attorney l -m i Patented Sept. .15, 1931 UNITED STATES PATENT OFFICE OTTO BAMBERGER, F DUISIBURG, GERMANY, ASSIGNOR TO DEUTSCHE MASCHINEN- FABRIK AKTIENGESELLSCHAFT, DUISBURG, GERMANY MANUFACTURE OF SEAMLESS TUBES Application filed March 25, 1926, Serial No. 97,328, and in Germany February 20, 1926.

This invention relates to a method for the manufacture of seamless tubes from hard material such as alloyed steels, special steels and the like.

Hitherto it has been necessary to manufacture such tubes by pressing and further treatment on draw benches owing to the hardness and sensitiveness of the material,

as the perforation of the blank by means of oblique rolling trains was rendered impossible owing to the hardness and nature of the material. The operation of drawing is therefore expensive and not econom ical, so that in consequence a high price was required for seamless tubes made from such material.

According to the present invention tubes from such material can be manufactured in a manner that is simple and at a reduced cost by the use of the pilgering process.

The novelty of the invention consists in first perforating the blank in a press to a thimble form, and then directly reducing it in diameter and thickness of wall on the draw bench to such an extent that it can be further treated in an immediately succeeding operation by finishing the rolling by pilgering.

The plant for carrying out the new process may by conveniently constructed so that the heated solid block coming from the furnace is first formed in the shape ofv a thimble in a press, and then, after the blank has passed through a heating furnace it is reduced in dimensions in a draw press, and after having had its closed end removed by means of a saw placed immediately behind the draw press it is again heated and passed.

on to the pilgering mill for final treatment. Flor this purpose it is advantageous to heat the blank in the heating furnace between the several pressing and rolling operations. In this way it is possible in contradistinction to the methods hitherto employed for the manufacture of such tubes, economically to pilger the blank in the manufacture of tubes of specially hard material or of tubes with special properties.

In the accompanying drawing is diagrammatically shown a' constructional example.

of a plant according to the invention.

As illustrated in the accompanying draw ing the press B serves to move the quadrilateral blocks which are brought up on a narrow gauge rail wagon to the furnace A in which they are turned several times so.

as to ensure their being well and uniformly I heated. Through the outlet door of ;the furnace A the blocks pass into a preliminary thimble-forming press C, in which they undergo a preliminary shaping into a form resembling a thimble. From the press C the-tubular blanks pass through a heating furnace D and thence into the draw press E, where the diameter and the thickness of the wall of the blank are reduced by one or more draw rings. As the blank emerges from the draw press E, a saw F placed behind the draw press cuts off the closed end. The tubular blank is then taken to another ,heating furnace G and passes out to the delivery or feedi apparatus H, which passes it on to the pllgering mill 3 In this latter the rolling of the tubes is completed, and they then pass by means of the delivery shoot L to the saw M which cuts off the ends. The train of rolls N conveys the tubes'or blanks to the bed 0 where they cool down.

I claim:

1. A method for the manufacture of seamless tubes of hard metals, such as alloyed steels and so-called special steels, consisting of the following steps in succession: the pressing of the heated blank of hard metal into the form of a thimble, reheating the thimble-like blank thus formed, drawing down the reheated blank and reducing the blank in diameter as wellas thickness of wall so as only partially to effect thereduction-of diameter and thickness required to produce the finished tube;- cutting off the closed end of the blank to produce a cylinder, again reheating the cylindrical blank and then reducin the reheated blank in diameter and thic ess to final dimensions in a pilgering mill, substantially as hereinbefore described.

2. A plant for the manufacture of seamless tubes of hard'metal such as alloyed steels and special steels according to the method of claim 1 consisting in combination of thefollowing apparatus in successive adjacent relation: a furnace adapted to heat the blanks of hard metal, a p'ress adapted to press the said blanks into a thimble form, a reheating furnace adapted to reheat the said pressed blanks, a draw press adapted partially to reduce the said pressed blanks in diameter and thickness 0f 7 wall, a saw adapted to remove the closed end from the said blanks, a further reheating furnace adapted to further reheat the said pressed, drawn and cut blanks and a pilgering mill adapted to reduce to final 'mensions of diameter and thickness the said pressed, reheated, drawn, and further reheated blanks, substantially as g herein before described.

. OTTO BAMBERGER. 

